One of the nastiest SEO practice is to spin content in many sites, re-publish articles, or generate crap from article directories while trying to improve PR and search ranking results.
Mainly we have to do site for people, not for Search Engines, as Gurus say. After Panda update these spamy techniques don’t work any more or not for a long time. Duplicating content may help you temporarily but not for long. Spinning one and the same content more than one time is completely wrong, regarding Google tips also. You could lose your PR and go away from first page results, because site will be penalized.
These practice are also very risky. When the search engine algorithm changes, you just disappear. This will cost you again more time to go back again and again….
Google is getting smarter and using user data to understand what people like which is the most important.
So people, don’t spin content, don’t duplicate content, don’t think of ranking factors! Make your site user-friendly and likeable. Instead loosing your time with black-heading, do something real and profitable.